The present invention relates to an Industrial Crane having an upper works rotatably mounted on a wheeled chassis.
Cranes have been developed and include many types, including cranes known as Industrial Cranes. Such cranes are used to pick up a heavy load and to transport the load to a different location, where the load is deposited. Industrial Cranes generally include a chassis supported by four rubber-tired wheels, the chassis including a bearing on which is mounted a rotatable upper works. The upper works is rotated, for example, by gearing, and includes a cab and a boom. The cab includes a seat for the operator, vehicular controls for controlling the propelling, steering and stopping of the vehicular chassis, and also includes crane controls for rotating the upper works about a vertical axis, for raising and lowering the boom, for extending and retracting the boom, and for operating a winch for the load cable. The power source for the Industrial Crane is typically an internal combustion engine, which may be placed either on or in the upper works, or on or in the chassis.
In a typical Industrial Crane, it is necessary to provide electrical circuits which extend from electrical components on or in the upper works to electrical components on or in the chassis. For example, in the operator's cab there may be switches which control lights mounted on the chassis. Typically, there are a plurality of electrical circuits which must extend between the upper works and the chassis and it is known to have, for example, six such separate circuits.
In order to permit the continuous operation of the Industrial Crane without interruption of the electrical circuits, there has been used an electrical connector of the "slip ring" type. Such electrical connectors are cylindrical, and have a plurality, for example six, axially spaced conductor bands provided on a rotary part of the connector, and contacts or "wipers" for engaging the conductor bands, which are stationary.
The above described electrical connector has been mounted on Industrial Cranes, and on similar industrial equipment, at the bottom of the swivel joint or bearing construction, or rotary hydrualic connector, as the case may be, extending therebelow, and being on the axis of the rotary bearing which supports the upper works. In known Industrial Cranes, for example, there have been provided a swivel joint assembly including a rotary oil coupling with the electrical connector below and coaxial with the rotary oil coupling and with the rotary bearings. The rotary oil coupling has been provided in order to provide a rotary connection for hydraulic oil between hydraulic elements in or on the upper works and in or on the chassis.
The placement of the electrical connector in the position noted is shown, for example Crabiel U.S. Pat. No. 4,177,869, Lexa Et Al. U.S. Pat. No. 1,809,981 and Turner U.S. Pat. No. 1,604,619. The foregoing patents are directed to cranes and construction machinery.
In all of the above described apparatus, the electrical connector has extended below the lowest part of the swivel joint, and in present day electrical connectors, this extension has been approximately five inches below the rotary oil coupling of the swivel joint. It has now been recognized that such an extension is undesirable, where the Industrial Crane is to satisfy the requirements of providing a boom and other supports of sufficient strength to support a desired load, to be of relatively low overall height, and to have a suitable ground clearance for the vehicular chassis, meaning that the vehicular chassis is able to transverse uneven ground with bumps. An example is the necessity for an Industrial Crane to travel up a ramp, and then move onto a level surface at the upper end of the ramp.
The cylindrical type electrical connectors above described, in which the conductor bands are arranged axially on a cylinder, are not the only type of electrical connectors known. There are known, also, a flat type of electrical connector in which the conductor bands are provided as concentric rings. Such electrical conductors are sometimes designated as the "pancake" type, and examples of them are shown in Nafziger U.S. Pat. No. 1,481,729, Dickerman U.S. Pat. No. 2,424,650 and Scott U.S. Pat. No. 2,725,540. However, flat or pancake electrical connectors are many times more expensive than are the cylindrical type electrical connectors.